I. Field of the Invention
The present invention relates to fluid flow monitors, and more particularly, to a fluid flow rate indicating assembly.
II. Description of the Prior Art
Fluid flow rate indicating assemblies have long been known. Typically, a member responsive to fluid flow is disposed in a housing through which the fluid passes. Flowing fluid impinges on the member, causing it to move. Often, the member is resiliently biased against such motion, so that movement of the member is indicative of the rate of fluid flow. Biasing means commonly employed include gravity or springs. Alternatively, the member can be a rotor, which is mounted on an axle having an end which passes through the housing, and which is connected to a tachometer. The rate of rotation of the rotor, as measured by the tachometer, corresponds to the rate of fluid flow through the housing. The type of indicator including a resiliently biased member also usually includes a shaft or other member passing through the housing, whose position can be correlated to the flow rate.
These known types of fluid flow indicators have encountered some drawbacks, however. Most notably, the perforation of the housing for the passage therethrough of a rotor shaft or other indicating shaft permits fluid leakage between the bore and shaft. This is usually met by disposing a packing about and between the shaft and housing bore. However, such packing is sometimes messy and occasionally unsuccessful. The packing is subject to wear, while the fluid being measured is subject to contamination from the packing material. The cost and difficulty of constructing packing structures which are resistant to high pressures increase as the fluid pressures encountered increase.